This invention relates generally to antennas, and more particularly to radio frequency reflective surfaces as used in conjunction therewith.
Antennas that radiate radio frequency energy are well known in the art. An unadorned antenna will typically radiate such energy in an omnidirectional fashion. It is also known to shape and/or specifically direct or steer the radiated energy towards (or away from) a particular area. For example, metal reflectors can be used to inhibit such energy from moving in a given direction. In addition, multiple antenna arrays can be manipulated, as with some proposed sectored antenna patterns and as implemented through baseband phasing techniques, to steer, at least to some extent, the radiated energy. Some such steering systems operate wholly electrically (as by phase adjustment and/or by switching various antennas in and out of operational modes), some wholly mechanical (as by rotor driven sector antennas), or combinations of both approaches.
Though suitable for at least some applications, the above solutions are not suitable for all contexts. Further, some of these techniques (and especially the more flexible approaches) are expensive and/or prone to maintenance problems (mechanically based systems utilizing moving mechanical parts are especially subject to these issues). Also, existing techniques, while potentially applicable for generally or specifically directing or blocking a beam of radio frequency energy in a given direction, are generally not useful for control of other potentially important performance parameters, including gain control and beamwidth control. Some combined solutions in this regard, such as use of omnidirectional antennas combined with multiple PIN diode driven scatterers, can effect beam steering and controllable beamwidth but are relatively expensive and further can cause switching spikes that can detrimentally impact system performance.